Electron discharge device



Dec. 15, 1936. V RONC] 2,064,320

ELECTRON DISCHARGE DEVICE Filed Feb. 27, 1930 ATTORNEY Patented Dec. 15,1936 UNITED STATES PATENT OFFICE Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application February 27, 1930,Serial No. 431,670

9 Claims. (01. 250-275) This invention relates to electron dischargedevices and more particularly to such devices of the screen grid type.

An object of the invention is to support a plurality of electrodes of anelectron discharge device in a unitary arrangement to obtain a highamplification constant and low inter-electrode capacity.

A further object of the invention is to improve the operatingcharacteristics of electron discharge devices.

A feature of the invention relates to the complete shielding of theelectrodes in an electron discharge device against extraneous magneticand electric fields.

Another feature of the invention relates to the electrode structure inelectron discharge devices whereby the electrodes will be free to expandwithout warping or changing their cooperative space relation.

A further feature of the invention relates to the protection of thevitreous portions of an electron discharge device against damage by highfrequency electric fields.

In an electron discharge device commonly known as the shielded orscreen-grid type there are several internal electrodes, one of which isin the form of a grid arranged to shield the control grid or electrode,for example, from the anode. In such devices the shielding should bethorough and the electrodes should be maintained in their proper spacedrelation in order to reduce the inter-electrode capacity. i a

In accordance with this invention the electron discharge devicecomprises a glass vessel having a stem from which all the elements aresupported by rigid members extending within the vessel, some of themembers forming the leading-in wires for the electrodes. A pair ofupright metallic rods support two spaced discs which form the endportions of a cage assembly that encasesthe electrodes in a totallyshielded arrangement. A cylindrical anode Within the cage assembly isinsulatingly supported by a rigid rod passing through anaperture in oneend disc and embedded in the stem and serving as the leading-1n wire forthe anode.

A pair of concentric grid electrodes are positioned'within the anode andcage assembly and spaced with respect to the plate electrode byinsulating discs supported on the metallic end discs.

-A cathode, either of the filament or indirect heater type, is. locatedwithin the anode and grid electrodes. This arrangement facilitates thefabrication of the multi-electrode assembly as a unitary structure inwhich all the elements are supported by the glass stem of the vessel,the electrodes are effectively shielded and the device operates withimproved characteristics.

These and other features of the invention will 5 be more apparent fromthe following detailed description with reference to the accompanyingdrawing in which Fig. 1 is a view in perspective of an electrondischarge device constructed in accordance with this invention withportions cut away to show the improved assembly and detailedconstruction of the electrodes;

Fig. 2 is a view of a unitary electrode assembly partly in section andpartly broken away showing the spacing and mounting of the electrodes inaccordance with this invention and embodying a cathode of theequipotential type;

Fig. 3 illustrates another embodiment of the invention similar to Fig. 2except that the anode 0 is formed of a wire mesh screen and the cathodeis in filamentary form;

Fig. 4 is a cross sectional view of Fig. 3 along line 4-4 showing thespace relation and shape of the electrodes;

Fig. 5 is a partial perspective view illustrating the mounting of theelectrode supporting structures upon the press; and

Fig. 6 is an enlarged cross-sectional view of the equipotential cathodeshown in Fig. 2.

Referring to the drawing, the electron discharge device of thisinvention relates to the screen grid type and comprises an enclosingglass envelope Ill and a base ll of insulating material attached theretoand provided with a plurality of prongs I! to serve as the externalterminals of the electrodes. The envelope I0 is formed with a reentrantstem portion terminating in a substantially rectangular press I3 fromwhich all the electrodes are supported. Two rigid metallic members'orrods l4 embedded in the press l3 are bent outwardly and upwardly nearthe press, as clearly shown in Fig. 5, and have parallel portionsextending substantially to the opposite end of the envelope' Hi to whichare attached two annular dish shaped metallic discs l5 and I6, eachprovided with a central oval opening and having their upturned edgesextending toward each other and positioned in spaced relation atopposite ends of the parallel extending portions of the rods I4. Anannular block or disc ll, of insulating material, such as porcelain,Lavite or similar material, is mounted upon the metallic disc l6 andserves as an insulating spacer for a plurality of relatively light withthe central oval aperture therein.

. the grid 2|.

rigid parallel upright wires l9 and i9 which extend between the discs l5and I9. The wires I9 pass at one end through the central oval aperturein the disc l6 to be slidably supported in the insulating disc l9 bysuitable spaced holes or slightly larger diameter than the wires and aretrictionally engaged at the other end in a small rectangular block 20 ofLavite, or other insulating material, having rounded ends which lie onthe side of the metallic disc I5 facing its associated metallic disc Itin axial alignm lelrlit e wires l9 extending parallel to and in the sameplane as the wires l9 and the rods I4 and located between them have oneend projecting from the insulating disc l1 and the other end piercingthe dish shaped metallic disc l5 and frictionally held therein by therough edged pierced opening surrounding the wires. The wires I9 alsofrictionally maintain the block 20 in position by engaging slots orgrooves in the rounded ends of the block 29. A helical wire grid 2|,preferably oi oval cross-section as shown in Fig. 4, has its turnsafilxed to the wires l8 and a second helical grid acting as a shieldinggrid 22 o! the same form as the grid 2| but oflarger diameter is mountedon the wires |9 concentrically with The shielding grid 22 iselectrically connected to the disc l6 and the supporting rods H by tiewires 23, shown clearly in Fig. 1, which extend across the disc l6through an undercut portion ofthe insulating disc l1 and are welded tothe wires l9 and rods ll.

Since the wires I8 and i9 are held in position at one end at least onlyby friction they are free to expand and contract without warping andtherefore the grids 2| and 22 are maintained in their proper cooperativespace relation at all times.

An anode 24, in the form oi! an oval shaped closed cylinder which may beof the solid plate type as shown in Fig. 1, is coaxially aligned withthe grid 2| and shield grid 22 and is supported by a single upright rod25 which extends through a large aperture in the disc l5 and is embeddedin the press IS. A cathode 26 which may be of the filamentary type asshown in Figs. 1 and 3 is arranged within the grid 2| and supportedbetween the insulating discs and 29. The cathode may be in the form ofan inverted V supported at its apex by a hook attached to a flexiblewire 21 extending from the top of the insulating block l1, and engagedat its extremities by wires 28 embedded in the insulating block 20,which pass through the oval central aperture in the metallic disc I5 andare welded to leading-in wires embedded in the press l3.

In order to shield the electrodes completely from all extraneouselectric and magnetic fields and improve the operating characteristicsof the device an outer helical wire shield 29 surrounds the mainelectrode structure and is supported between the discs I5 and 5 by rigidwires 30 and electrically connected to the shielding grid 22 and thediscs I 5 and I9 by the tie wires 23, the ends of the shield 29 restingwithin the upturned edges of the metallic discs l5 and IS. The wires 3!]are held in position at the lower end by frictional engagement in closefitting apertures in the disc IS in a similar manner to the positioningof grid wires I9 and are' free to expand and contract without warping. Aleading-in wire 3| for the control grid 2| is sealed into a portion 32in the top of the envelope l9 and the end thereof within the vesselisattached to one of the wires l9 and the outer end is connected to ametallic cap 33 which is cemented to the glass vessel Ill and serves asan external terminal for the grid 2|. A metallic disc 34 having aU-shaped bracket portion 35 integral therewith is located near the discl5 and carries a pellet 36, or getter material, such as magnesium whichwhen vaporized absorbs the residual gases in the device.

This arrangement provides a compact and rigid electrode structurewhereby all of the electrodes are supported entirely from the press andwhich is easily assembled at small cost. The supporting wires for thegrid 2| and the shields 22 and 29 are all free to expand when subjectedto heat and are arranged along a diameter of the structure therebymaintaining symmetry oi. the electrodes at all times. Furthermore, theelctrodes are completely and effectively shielded from extraneousmagnetic and electrostatic fields by the complete cage like shieldingstructure comprising the closely wound helical shield 29 and the solidend discs l5 and IS. The electronic field is confined to the spacebetween the electrodes and this together with the reduction ininter-electrode capacities effected by the spacing arrangement of theelectrodes provides an electron discharge device having improved anduniform characteristics. While the main object of the completecage-:like shield around the electrodes is to protect the electrodesfrom extraneous interference with the travel of electrons between theelectrodes, the end disc portions of the shield serve to rigidlymaintain the various parallel supporting wires of the electrons inuniform space relation so that the tube characteristics depending onelectrode interrelation do not change during transit or operation of thedevice. The metallic disc near the stem also provides means forrelieving the electrode supporting wires from strain due to expansionsince these wires may readily slide through the friction openings inthis disc. Furthermore, the lower disc prevents a conductive depositforming on the glass stem between the leading-in wires of the low andhigh potential electrodes such as the filament and plate electrodes,thereby prolonging the life of the device.

Another embodiment of this invention is shown in Fig. 2 in which thearrangement and mounting of the electrodes and shielding cageconstruction is combined with an equipotential type cathode in anelectron discharge device. This cathode comprises a drilled quartz rod31, shown in crosssection in Fig. 6, through which a heater wire 38 isthreaded, and a metallic sleeve 39 crimped on the rod 31 and coated witha thermionically active material, such as alkaline earth oxides, capableof emitting electrons when heated. The manner in which externalconnection to the cathode is made is shown in Fig. 5. Leading-in wireslllfor the heater element are connected to the ends'of the wire 38,sealed in the press |3 and connected to the desired pair of the prongsl2, and a leading-in wire 4| is connected to an integral extendingportion 42 of the sleeve 39 and also embedded in the press I3 andconnected to one of the prongs I2.

Figs. 3 and 4 show another embodiment of this invention in which a meshtype anode 43 is supported on a rod 44, the anode beingconcentric withthe control grid 2| and shielding grid 22. The mesh type oi. anodereduces considerably excessive heating of the anode due to bombardmentby electrons. It is, of course, understood that the cylindrical portionof the shield 29, as shown in Fig. 1, may also be formed or a wire meshsimilar to the anode 43 to increase the rigidity of the assembly.

While various embodiments of the invention have been disclosed anddescribed it is understood that various modifications may be made in thedifferent assemblies shown without departing from the scope of theinvention as defined in the appended claims.

What is claimed is:

1. An electron discharge device comprising a container, a plurality ofelectrodes supported therein, a pair of supporting members extendinglengthwise of said container, and a metallic cage structure completelyenclosing said electrodes, and comprising two spaced annular dish shapedmembers mounted on said supporting members, a single pair of rodsextending between said dishshaped members and attached thereto, and awire screen mounted on said rods and seated within said dish-shaped,members.

2. An electron discharge device comprising a container, a plurality ofelectrodes mounted con.- centrically therein, a metallic shieldcompletely enclosing said electrodes and comprising a pair of spaceddisc members each having an inwardly directed peripheral flange mountedat right angles to the axis of said electrodes and a metallic screenseated at each end within said flanges surrounding said electrodes andconcentrically disposed therewith, said screen and discs beingelectrically connected to one of said electrodes, an insulating platemounted within said shield and seated on one of said disc members,another insulating plate mounted exterior to said shield and seated onthe other disc member, and means on a plurality of said electrodes incontact with the insulating plates.

3. An electron discharge device comprising a cathode, grid, and plateelectrode, a cage electrode substantially surrounding said electrodescomprising two end discs and a metallic screen supported therebetween, adisc insulating member seated on and carried by one of said discs andsupporting said cathode and said grid at one end, and another electrodepositioning said insulating member on said one disc.

4'. An electron discharge device, a mount comprising a press, a pair ofupright members embedded in and extending from said press, a metallicdisc mounted between said members, an insulating plate adjacent saiddisc, a resilient .member carried by said plate, a second metallic discmounted between said upright members, an insulating block adjacent saidsecond disc, and an electrode supported between said discs by saidresilient member and said insulating block.

5. In an electron discharge device, a mount comprising a press, a pairof metallic disc members supported in spaced relation therefrom, aninsulating member adjacent each of said disc members, a resilient membermounted on one of said insulating members, a plurality of metallic rodsextending through the other of said insulating members and frictionallyengaged therein, and an electrode supported between said disc andinsulating members by said resilient member and said rods.

6. In an electron discharge device, an electrode assembly comprising apress, a plurality of electrodes supported from said press, two bent rodmembers embedded in said press, each of said members having a straightportion parallel to the longitudinal axis of the device, two metallicdisc members attached in spaced relation between the straight portionsof said rod members, a straight metallic member adjacent the straightportion of each of said rod members, and a shield between said rodmembers, supported on said straight metallic members and seated in saiddiscs and surrounding said electrodes.

'7. An assembly for electron discharge device, including a press, anelectrode supported therefrom, and a cage type shield for said electrodecomprising a pair of metallic disc members supported from said press, aspacing member of insulating material parallel to and adjacent each ofsaid disc members,- a pair of metallic rods supported between'said'spacing members at right angles thereto, and a cylindrical metallicscreen mounted on said rods and joined to said metallic disc members. I

8. An electron discharge device comprising an enclosing vessel having astem, a plurality of supporting members extending from said stem, a pairof spaced metallic discs transverse to the axis .of said vessel rigidlyattached to said members, a

plurality of supporting Wires mounted in a single plane between saiddiscs and supported directly by said discs, and individual coaxialelectrodes carried by said supporting wires.

9. An electron discharge device comprising an enclosing vessel having astem, a plurality of upright rods extending from said stem, a pair ofparallel dish-shaped members mounted in spaced relation on said rods, aninsulator carried by each of said dish-shaped members, a' cathodesupported between said insulators, a pair of rigid wires extendingbetween said insulators and-positioned thereby, an electrode mounted onsaid wires and disposed about said cathode, a pair of supports carrieddirectly by said dish-shaped members, and a screen electrode carried bysaid supports, seated. at each end in said dish-shaped members andsurrounding said cathode and said first mentioned electrode.

VICTOR L. RONCI.

